ZY19489 resistance creates collateral hypersensitivity, neutralizing PfCRT-mediated drug efflux and restoring antimalarial activity

The global fight against malaria faces a critical challenge with the widespread emergence of Plasmodium falciparum parasite resistance to current artemisinin-based combination therapies. This resistance often involves the P. falciparum chloroquine resistance transporter (PfCRT), a transmembrane protein that mediates the efflux of antimalarial drugs from the parasite's digestive vacuole, thereby reducing their intracellular concentration and efficacy. New drug candidates and strategies are urgently needed to overcome PfCRT-mediated resistance and extend the lifespan of existing antimalarials.

Researchers characterized ZY19489, a novel triaminopyrimidine currently in a Phase Ib clinical trial, using in vitro asexual blood-stage Plasmodium falciparum parasites. They generated ZY19489-resistant parasite lines by pressuring cultures with increasing drug concentrations. The study then assessed the susceptibility of these resistant lines to other antimalarial drugs, including piperaquine and chloroquine. Metabolomic studies were performed to analyze changes in intracellular metabolite profiles, specifically focusing on hemoglobin-derived peptides, to elucidate the mechanism of action and resistance.

Resistance to ZY19489 was found to induce a phenomenon of collateral hypersensitivity, effectively neutralizing PfCRT-mediated drug efflux. This mechanism specifically blocked the efflux of piperaquine and chloroquine, thereby restoring their antimalarial activity against Plasmodium falciparum strains that were previously resistant due to PfCRT mutations. This suggests an 'evolutionary trap' where resistance to one drug makes the parasite vulnerable to others. > Metabolomic studies revealed that ZY19489 treatment significantly reduced intracellular levels of short hemoglobin-derived peptides, which are natural substrates for PfCRT. This reduction in PfCRT substrates is hypothesized to be central to the observed collateral hypersensitivity, as it alters the transporter's function and substrate specificity, leading to the blockade of other antimalarial efflux.